26.D
We’ll go to hear the famous singer (whom/that/who) we have often talked about.含有介词的动词短语一般不拆开使用,如:look for,look after,take care of等
31.A
as 和which在引导非限制性定语从句时,这两个关系代词都指主句所表达的整个意思,且在定语从句中都可以作主语和宾语.但不同之处主要有两点:
(1) as 引导的定语从句可置于句首,而which不可.
(2) as 代表前面的整个主句并在从句中作主语时,从句中的谓语必须是系动词;若为行为动词,则从句中的关系代词只能用which..